we agree on that but you just type it
Combi Boiler - Performance Question
- Thread starter CanYouHelpMe
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The difference is that my "pish" is an opinion based on experience ( mine and other people's ) and is typed with the aim of giving the other side of the story.
The pish from marketing is aimed at leading people into making decisions which lead to increased sales.
But boiler specs state the output into the water (under specified conditions, naturally). That, with the stated gas flow and efficiency tally OK, the ones I've looked at. If the boiler output is set below maximum, that needs checking, or if the water flow is low due to low pressure, the gas input will reduce to maintain set temperature. On a new boiler it's unlikely IMO that output is low due to efficiency being below spec.
I know boiler efficiency is your thing
but you've lost me there. Efficiency is the heat into the water (easy enough to measure, flow x temperature rise) divided by heat in from the gas (GCV or NCV being stated). What do you mean by efficiency of combustion? I would assume combustion is effectively complete, and if it isn't the result would be lower efficiency on test (and quoted in the data sheet).PS I meant to add - with the litany of problems the OP has described, these things are most likely the least of his worries.
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H
Hot&Cold
this thread has moved on so much,maybe not so informative to CanYouHelpMe as the armchair and reply robots of no competence have made comments.
CanYouHelpMe,your new boiler can be adapted to your existing system and the shower issue rectified. CanYouHelpMe dont worry there is often some topic variation to be aware of.
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But is the actual measured gas flow the same as the stated gas flow for a particular set of specified conditions. Do those specified conditions include the temperature and humidity of the incoming air for combustion. And more important does the testing house set up specified conditions that ( maybe according to the manufacturer ) will give the highest efficiency figures
Does the tally include the rise in temperature and volume of combustion air passing though the boiler ?
Unless the boiler output has been set low for some reason, there's no reason why it wouldn't be. And it's easy enough to check, just read the meter over a timed minute, or longer for higher accuracy.
But even if gas flow is low, it's that which might be causing the low hot water performance, not boiler efficiency being below spec.
As I said in earlier post, I assume testing would be under specified conditions - flowrate, temperature rise, flow temperature etc, to give comparable figures between manufacturers, but I don't know full details. Maybe incoming air temperature, but I doubt whether normal variation of RH would cause a measurable difference. I don't think it was ever explained how somebody claimed 126%, but that's been beaten to death.
It's irrelevant. If the heat into the water, and the heat in the gas are determined, dividing one by the other gives efficiency. For a given boiler on test, the rise in temperature and volume of combustion air are what they are.
I still don't think it's possible, or necessary, to split boiler efficiency into combustion and transfer efficiency. Dividing out by in gives overall efficiency.
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